Reproductive behaviors (e.g., estrous behavior, maternal behaviors) and regulatory behaviors (e.g., food intake, voluntary exercise) are intricately interrelated with one another. Both are sensitive to the same sorts of influences, such as hormones and changes in energy balance. Common neural loci may control reproductive and regulatory behaviors and integrate them with endocrine and metabolic responses. For example, reproductive hormones (e.g., estradiol, progesterone, prolactin) influence both reproduction and behavioral regulation of body weight and composition. Conversely, both regulatory behaviors and reproduction are sensitive to changes in the supply of utilizable metabolic fuels. The focus of this research program is the interaction between energy balance and reproduction--both the effects of reproductive hormones on regulation of energy balance and the effects of energy metabolism on reproduction (particularly reproductive behaviors). One group of experiments will focus on the sites and mechanisms by which reproductive hormones act to affect body weight regulation. Intracerebral hormone implants will be used to determine the neural loci where hormones act to influence food intake and energy expenditure. Metabolic responses in brown and white adipose tissues will also be examined, because reproductive hormones effect the storage and utilization of metabolic fuels. Particular attention will be paid to species differences in behavioral and metabolic effects of hormones, because some species differ from rats in their body weight responses to hormones (e.g., Mongolian gerbils and Siberian (Djungarian) hamsters). these animals may be more appropriate animal models for hormone effects on human body weight regulation than rats are. Another group of experiments will examine the effects of manipulations of the availability of metabolic fuels on reproductive and regulatory behaviors as well as estrous cyclicity in Syrian (golden) hamsters. Metabolic fuel supplies will be altered in several ways, including: a) food restriction, b) the use of inhibitors of glycolysis and fatty acid oxidation (2-deoxy-D- glucose and methylpalmoxirate), c) induction of diabetes mellitus, d) manipulation of energy utilization for thermoregulation and exercise. An attempt will be made to determine whether adipose tissues can serve as an energy buffer and spare reproductive processes from any of these manipulations.